json8-patch/lib/compile.js

JSON Patch toolkit for JavaScript

"use strict";

var decode = require("json8-pointer/lib/decode");

var patch = [
  { op: "add", path: "/a/b/c", value: ["foo", "bar"] },
  { op: "remove", path: "/a/b/c" },
  { op: "replace", path: "/a/b/c", value: 42 },
  { op: "move", from: "/a/b/c", path: "/a/b/d" },
  { op: "copy", from: "/a/b/c", path: "/a/b/e" },
  { op: "test", path: "/a/b/c", value: "foo" },
];

var doc = { a: { b: "foo" } };

function pathToStatement(path) {
  var tokens = decode(path);
  var statement = tokens.shift();
  tokens.forEach(function (token) {
    statement += '["' + token + '"]';
  });
  return statement;
}

function compile(patch) {
  var code = "";
  patch.forEach(function (op) {
    var o = "";
    switch (op.op) {
      case "remove":
        o += "delete " + pathToStatement(op.path);
        break;
      case "add":
        o += pathToStatement(op.path) + " = " + JSON.stringify(op.value);
        break;
      case "replace":
        o += pathToStatement(op.path) + " = " + JSON.stringify(op.value);
        break;
      case "move":
        var from = pathToStatement(op.from);
        o += pathToStatement(op.path) + " = " + from + ";\n";
        o += "delete " + from;
        break;
      case "copy":
        o += pathToStatement(op.path) + " = " + from;
        break;
      case "test":
        o +=
          "if (!oo.equal(" +
          pathToStatement(op.path) +
          ", " +
          JSON.stringify(op.value) +
          ") throw new Error()";
        break;
    }
    code += o + ";\n";
  });
  return code;
}

console.log(compile(patch));